Defects Enriched p‑type Zinc Stannate for Selective\nDetection of ppb-Level NO<sub>2</sub> Gas at Ambient Temperature

In\nthis study, we explore the synthesis and gas-sensing capabilities\nof zinc stannate (Zn<sub>2</sub>SnO<sub>4</sub>) in three morphologiesspherical\nnanoparticles, urchins, and octahedronsaiming to investigate\nthe influence of morphology on sensing properties. The fabricated\ndevices exhibit a significant resistance decrease upon exposure to\nNO<sub>2</sub> at room temperature (24 °C), indicating p-type\nsensing behavior. Among these morphologies, the spherical nanoparticle-based\nsensor exhibits the highest sensor response of 57% to 6 ppm of NO<sub>2</sub>, outperforming urchins and octahedrons by approximately 1.2\nand 4.1 times, respectively. This superior performance, with response\nand recovery times of 6.3 s and 224 s, is attributed to enhanced redox\nreactions from a larger surface area and a higher proportion of oxygen\ninterstitials. The spherical nanoparticle-based sensor also demonstrates\nexceptional selectivity for NO<sub>2</sub> over SO<sub>2</sub>, CO,\nNH<sub>3</sub>, and CH<sub>4</sub>, with a detection limit of 200\nppb. Furthermore, the sensor exhibits excellent reversibility with\nonly 2% variation across 20 consecutive test cycles and demonstrates\nremarkable long-term stability, with a performance fluctuation of\napproximately 2.3% over 63 days without significant degradation.